The goal of this Phase II program is develop, test and produce a prototype field analytical instrument for electrochemical monitoring of arsenic in drinking water. This program seeks to provide a new avenue to laboratory-quality arsenic detection and quantification in a field-portable device at reasonable cost. The long term vision for this technology is that it will become a key environmental science tool to support the development of strategies to prevent arsenic-related disease in individuals and population and to help people liver longer, healthier lives, a key aspect of the mission of NIEHS. We envision this technology also having a role in the international arsenic contamination picture, particularly in countries such as Bangladesh, where over 70% of drinking water wells contain toxic concentrations of arsenic. Specific Aims of the Phase II program will include design and construction of a prototype field-portable analytical system for detection of arsenic in drinking water at concentrations between sub-ppb and many ppm. The performance of the instrument will be characterized in the lab for the effects of real sample issues, including several classes of interferences and environmental variables. Once fully characterized, the prototype will be tested in the field with selected stakeholders in the drinking water distribution system arena. The new prototype technology will be benchmarked against standard analytical laboratory methods and other available field tests, such as colorimetric kits. During Phase I, favorable comparison to standard analytical laboratory analysis has already been obtained on drinking water samples from New Mexico and remediation treatment process water from Nevada. These results provide high confidence that the proposed analytical methodology will be an effective tool to prevent arsenic related disease from drinking water exposure. In the United States and globally, contamination of drinking water by naturally occurring arsenic puts populations at risk of a variety of arsenic-related diseases. The proposed Phase II program will provide a cost- effective and highly accurate way to monitor arsenic in drinking water at the site of the water source. The long- term vision for this technology is that it will become a useful tool for helping to arsenic-related disease among exposed populations. [unreadable] [unreadable] [unreadable] [unreadable]